Ozone filter material

ABSTRACT

An ozone filter material, with a long-lasting ozone degradation capacity, comprising a non-woven fabric filter material containing 200-600 g/m 2  of activated charcoal impregnated with 0.1-5 wt. % of an organic acid and 0.1-5 wt. % of a bromide and/or iodide salt.

FIELD OF THE INVENTION

The present invention is directed to an ozone filter material having along-lasting ozone degradation capacity.

Because of its toxicity and environmentally damaging properties, ozoneformed during ionization processes must be degraded. Ozone is producedin various air-purification systems to help reduce unwanted odors in theair or the growth of microorganisms. In order to degrade the remainingozone, an ozone filter medium composed of an activated carbon layer istypically used.

BACKGROUND

From the document JP 57177327, a device is known for reducing odors, inwhich the air mixed with ozone is directed through a filter impregnatedwith an aqueous bromide and or iodide solution and is subsequentlydirected through a layer of activated carbon.

However, the ozone degradation capacity of activated carbon decreasesalready after a short period of time, so that maintaining the ozonedegradation capacity either requires a filter change or, however, aquantity of activated carbon that will ensure a sufficient ozonedegradation for a longer period of time. In any case, however,disadvantages arise with respect to the costs entailed, since eitherfilters must be frequently replaced or, due to the pressure differenceat the filter, more energy must be expended in order to transport thegas through the filter medium.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an ozone filtermaterial which will have the feature of a distinctly prolonged usefulservice life with respect to ozone degradation capacity as compared tofilter materials having comparable filter engineering parameters, suchas pressure difference or activated carbon content.

The objective is achieved in accordance with the present invention by anozone filter material which is made of a nonwoven material and contains100-800 g/m² activated carbon, the activated carbon being impregnatedwith 0.1-5 weight % of an organic acid and 0.1-5 weight % of a bromidesalt and/or iodide salt. Such an ozone filter material is distinguishedby a long-lasting, virtually constant ozone degradation capacity ascompared to other filter materials.

The ozone filter material according to the present invention preferablycontains activated carbon that is impregnated with 0.5-3 weight % of amultivalent organic acid and 0.25-1.5 weight % of an alkali oralkaline-earth metal bromide and or of an alkali or alkaline-earth metaliodide.

Especially preferred is an ozone filter material which containsactivated carbon impregnated with citric acid and potassium iodide.

The ozone filter material according to the present invention ispreferably formed in such a way that the activated carbon is introducedbetween two nonwoven fabric layers.

Especially preferred is an ozone filter material in which the activatedcarbon is bound to the nonwoven fabric layers through the use of abinding agent. In this context, the nonwoven fabric layers arepreferably composed of synthetic fibers or filaments.

Finally, the present invention relates to the use of an ozone filtermaterial in commercial fresh-air filters, passenger compartmentfresh-air filters or in filters used in ventilation purificationsystems.

The present invention is explained in greater detail in the following onthe basis of two comparative examples.

EXAMPLE

An activated carbon granulate, which has a particle size that passesthrough a screen having 30×70 mesh size is impregnated in each case withaqueous solutions of citric acid and potassium iodide in such a waythat, in the dry state, it contains 1.0 weight % citric acid and 0.5weight % potassium iodide. The impregnated activated carbon is mixedwith a binding agent and is applied in a spraying process in a quantityof 400 g of activated carbon/m² to a nonwoven fabric filter material andcovered with another nonwoven fabric filter layer. Subsequently to thepleating and folding process, a filter medium is obtained which, given afilter surface area of 0.164 m², contains 65 g of activated carbonquantity.

Comparative Example 1

The activated carbon granulate in accordance with Example 1 isimpregnated with an aqueous solution of potassium iodide in such a waythat, following the drying operation, the activated carbon contains 0.5weight % of potassium iodide. The processing into a filter material iscarried out analogously to Example 1.

Comparative Example 2

Activated carbon granulate in accordance with Example 1 is processedanalogously to Example 1 into a filter medium.

Illustration 1 shows the ozone degradation capacity of Example (B1) andof comparative Examples (V1, V2) obtained using the manufactured ozonefilter media. In the process, the test was performed in a flow channelhaving a flow rate of 1.5 m/s and a volumetric flow rate ofapproximately 100 m³/h under laboratory conditions and at a roomtemperature of approximately 23° C. On the unprocessed air side, aconstant ozone concentration of 750 ppb (+/−50 ppb) was set using acommercial ozone generator. The filter medium according to the presentinvention exhibits a continuously low ozone gas concentration (K in[ppb]) on the cleaned gas side (degradation capacity approximately 93%following 3.5 days [d]), while the comparative examples only yielded 86%and, respectively, approximately 73% ozone degradation after three daystest duration.

1-7. (canceled)
 8. An ozone filter material comprising: a nonwovenfabric filter material containing 100 to 800 g/m² of activated carbonimpregnated with 0.1-5 weight % of an organic acid and 0.1 to 5 weight %of a bromide salt and/or of an iodide salt.
 9. The ozone filter materialas recited in claim 8 wherein the activated carbon is impregnated with0.5-3 weight % of a multivalent organic acid and 0.25-1.5 weight % of analkali or alkaline-earth metal bromide and/or of an alkali oralkaline-earth metal iodide.
 10. The ozone filter material as recited inclaim 8 wherein the activated carbon is impregnated with citric acid andpotassium iodide.
 11. The ozone filter material as recited in claim 8wherein nonwoven fabric filter material includes two nonwoven fabriclayers, the activated carbon being located between the two nonwovenfabric layers.
 12. The ozone filter material as recited in claim 11wherein the activated carbon is bound to the nonwoven fabric layersthrough a binding agent.
 13. The ozone filter material as recited inclaim 11 wherein the nonwoven fabric layers are composed of syntheticfibers or filaments.
 14. A method for utilizing the ozone filtermaterial as recited in claim 8, the method comprising placing the ozonefilter material in commercial fresh-air filters, passenger compartmentfresh-air filters or in ventilation filters.